An electrostatic image recording system of the transfer type uses a record medium in the form of an endless belt. The endless record medium is of laminar configuration and includes a film, or coating, of a dielectric substance which is to be electrostatically charged to serve as a recording layer. This endless record medium is driven to travel between two spaced, parallel rollers through a record zone established by a record head in which a multiplicity of electrodes each in the form of a stylus are arranged in an array or arrays perpendicularly to the direction of travel of the belt. These stylus electrodes are electrically connected to a source of positive or negative pulses and are selectively actuated with pulses produced on the basis of the data signals generated externally of the system. When the stylus electrodes are thus selectively actuated during a line print cycle, positive or negative charges are produced in a single line on the surface of the dielectric film of the record medium which has been preliminarily charged or discharged uniformly throughout its width. The charges thus produced on the record medium by means of the record head form a line of electrostatic latent images in dot form on the dielectric film of the record medium. The latent images are developed by application of a toner to the surface of the dielectric film and the resultant pattern of the dots of the toner particles thus deposited on the charged surface of the record medium is then transferred to a sheet of paper brought into contact with the image-carrying surface of the record medium. The pattern of the toner particles transferred to the sheet of paper is fixed by application of heat thereto at a subsequent fixation stage.
After the pattern of the toner has been transferred to the sheet of paper, the endless record medium is passed to a cleaning stage and is cleaned to remove the traces of the toner particles remaining on the record medium as well as the residual charges on the medium for being ready for use in the subsequent line print cycle. It is, however, extremely difficult and even practically impossible to perfectly remove the traces of the toner from the surface of the record medium. Thus, the record medium which has passed through the cleaning stage of the system still has traces of the toner particles which have failed to be removed from the medium at the cleaning stage. The toner particles remaining on the dielectric film of the record medium may be transferred to the tips of the stylus electrodes of the record head and may consequently spoil the quality of the images or prints to be finally printed on a sheet of paper. The deterioration in the discharge performance of the record head may further result in production of unnecessary prints or stains on the sheet of paper in addition to the prints resulting from the proper latent images produced on the record medium. This will also results in degradation of the quality of print on the paper.
It is, accordingly, an important object of the present invention to provide a novel method of cleaning the record head of an electrostatic image recording system of the transfer type.
It is another important object of the present invention to provide a novel method of cleaning the record head of an electrostatic image recording system of the transfer type by precluding transfer of toner particles from the record medium to the record head after patterns of the toner particles deposited on the record medium have been transferred to a record sheet and the traces of the toner particles remaining on the record medium have been largely removed from the record medium at the cleaning stage of the system.